The proposal is still accepted. When we attempted to integrate the implementation last, we ran into linkage issues with the backward-deployment compatibility libraries, as well as some issues with ptrauth integration. Unfortunately we haven't since had time to investigate those issues on our end to complete the integration, and concurrency work has saturated most of the core team's bandwidth. I would personally still like to see this get integrated sooner than later. Now that we've implemented availability for conformances, the backward compatibility part of the implementation could be separated out from the core implementation, allowing us to integrate that first and address backward deployment separately.